21.02 March 2011

Eyes On The Prize

Just like any other muscle in the body, extraocular muscles in the eye get stronger with training. Athletes at the United States Air Force Academy have been reaping the benefits of a sports vision training program for more than a decade.

By Dr. Michael Zupan & Al Wile

Michael Zupan, PhD, is Director and Al Wile, MS, is Assistant Director of the United States Air Force Academy's Human Performance Laboratory. For more information about the Lab, go to: www.goairforcefalcons.com and click on "Performance Lab" under the "Inside Athletics" drop-down menu.


How much can sports vision training improve an athlete's performance? This is by far the most common question we receive here in the Human Performance Laboratory at the United States Air Force Academy. Unfortunately, we cannot quantify exactly how much sports vision training will increase a baseball player's batting average, a basketball player's shooting percentage, or a goalie's save percentage.

But we can tell you that in 1995, the first year we implemented a six-week training program for our baseball players, the team led the nation in hitting and slugging percentage. We can also tell you that the data we've collected show anywhere from 24 to 114 percent improvement in athletes' visual-motor performance over the course of their playing career at the USAFA.

Finally, we can tell you what our athletes and coaches think about it. Our baseball players say that they are able to pick up the spin of the ball coming out of the pitcher's hand earlier, other athletes say that their eyes don't fatigue as quickly, and our coaches end up wanting their players to start coming in year-round instead of only during the off-season because they've noticed a difference in their athletes' performance.

Here at the USAFA, vision training is an integral part of performance enhancement. In our mandatory six-week off-season program, athletes train for 15 to 20 minutes at least three times a week. After each training session, we update each athlete's file. Currently, we have a vision training database that includes data from over 2,000 athletes--some with over 100 training sessions throughout their four-year playing career--and it shows tremendous improvements in all of our athletes' visual-motor performance.

Although there are a variety of different sports vision training programs in which an athlete sits down at a computer to use a software program, we feel the best results come when athletes most closely mimic the specific demands of their sport. Having athletes engage in sport specific behavior while training the eye establishes neural connections between the brain and the body's large muscle groups, which is very important for making improvements on the field, court, or ice.

Walk into the Human Performance Lab, and you might see one of our athletes training in their playing stance--for example, a soccer goalie in a crouched position anticipating a shot on goal. Training in this life size, sport-specific mode allows the athletes to better integrate all their peripheral sensory inputs, including the vestibular system (which helps the body maintain good balance) and muscle proprioceptors (which help promote spatial awareness).

Think of sports vision training as an extension of athletic motor skill development. To increase performance, athletes must develop visual motor skills throughout their careers to allow the eyes to perform effectively and efficiently. The idea is similar to motor skill development for a baseball swing. A baseball player develops his swing throughout his career based on visualization and motor input from his last game, batting practice, or coach's advice. This same progression occurs in the eyes.

Most of our work strives to increase the endurance of the six extraocular muscles, which results in a decrease in eye fatigue that may occur during a game or over the course of a long season. The extraocular muscles, like any other striated muscles, tire when stressed. All athletes work their eyes during practices and games, but our 20-minute vision training session specifically overloads the extraocular muscles. These muscles then respond by getting stronger and becoming more resistant to fatigue.

As athletes progress and begin to master the exercises, distractions are added to increase the level of difficulty. These include having several athletes training at the same time call numbers out loud, playing loud music in background (sometimes music they like, sometimes music they don't), having people walk around and in front of athletes, and using modalities such as a BOSU ball, mini trampolines, or balance boards.

The exercises we choose for our athletes concentrate on six areas: saccadic (rapid) eye movement; eye-hand speed and coordination with central peripheral awareness; stereopsis and depth perception; dynamic visual acuity; accommodation; and visual memory, focus, and concentration. In all six areas, we use established exercise physiology principles such as individuality, specificity, and progressive overload with the overall intent to fatigue the eyes so they will recover and be stronger.

Saccadic eye movement: Saccade exercises improve muscular endurance and help athletes improve their ability to focus on a single spot or object, like a baseball coming out of a pitcher's hand or a lacrosse ball coming toward them. We use both horizontal and vertical saccade exercises to train athletes to move their eyes quickly and efficiently from target to target while enhancing their visual processing abilities.

In our drills, an athlete stands in their athletic position eight feet from a wall. On the wall directly in front of them are two vertically-aligned letter charts placed 10 feet apart. Looking at the chart on the left, the athlete reads the first letter out loud, then quickly moves his or her eyes to read the first letter on the right chart. The athlete then repositions their eyes back to the left chart to read the second letter, then the second letter on the right chart, and repeats the sequence for two 60-second intervals. Calling each letter out loud ensures the athlete is reading the correct letter and fully processing the image. The athletes do this with horizontal charts as well, with one placed 10 feet above the other.

The athlete must do this exercise without moving his or her head--only their eyes. As the athlete progresses, we move the charts further apart, forcing the eyes to span a greater distance. We'll separate the horizontal charts up to 16 feet and the vertical charts as far as we can before they hit the ceiling.

Eye-hand speed and coordination with central peripheral awareness: A skill vital to all athletes, especially goalies, eye-hand coordination needs to continually be developed. And for the athlete on the soccer field or ice rink, peripheral awareness allows them to be aware of teammates open for a pass or opponents coming toward them while maintaining concentration on handling the ball or puck.

Our athletes use several eye-hand training devices, all similar in nature. They include the Accuvision 2000, Dynavision D2 Sport Vision Trainer (SVT), Wayne Saccadic Fixator boards, and the Makoto Arena. These boards have targets to strike when they light up: The D2 has raised buttons, the SVT has a 2.5-inch target, and the Accuvision has a one-inch target.

We start each exercise at a low speed and increase the pace once an athlete hits 80 percent of the targets at a given speed. During these exercises, we emphasize the importance of keeping the head still and the eyes fixated on the center of the boards. We ask them to do this because it increases their peripheral awareness for the distance lateral targets.

Stereopsis and depth perception: Several of our exercises work to improve binocular vision, which results in better stereopsis and depth perception. Stereopsis is the processing of the slightly different images each eye sees while looking at something to determine depth. For example, a right-handed batter standing at the plate may have his right eye three inches behind his left eye when looking at a pitch, yet the brain decodes the two slightly different images and allows him to determine where the ball is in flight. The batter then decides exactly where to swing the bat.

Good depth perception allows athletes to judge where objects are in space, including estimating distances accurately. Have you ever wondered why some great running backs never return punts or kickoffs? It may be because they have difficulty following the football over a long distance due to poor depth perception and/or tracking skills.

One of the simplest exercises to improve stereopsis and depth perception is the Brock string exercise. The Brock string is a 20-foot length of string with colored beads on it spaced four feet apart. While the athlete holds the string at the tip of their nose and the other end is attached to a fixed point in front of them, they begin by looking at the first bead. If they have excellent depth perception, they should see two strings coming into the bead at the vertex and two strings exiting directly behind the bead. It should look like an X with the bead right in the middle.

An athlete who sees the strings meeting three inches short of the bead needs to train his or her eyes to relax and gaze further into the distance. When they do this, they will actually see the X will move toward the bead. If this athlete were a basketball player, the initial visual input would have caused him to perceive the hoop to be closer than it actually is. If he trains on this exercise long enough, his eyes will become "retrained" to focus on the hoop at the right depth.

This exercise gives immediate feedback to athletes on how well their eyes are "working" that day. And we've found that accuracy varies based on how much sleep an athlete has gotten during the week or how much stress their eyes have been under.

We have also modified this exercise to be sport specific. For example, our basketball players use longer strings that are attached 10 feet in the air (the height of a regulation basketball hoop) to help with their shooting accuracy. And baseball infielders and soccer players hook the string near the bottom of a wall and do the exercise with a downward gaze.

Our program at the USAFA has been so successful improving depth perception that our base optometry clinic sent us 10 cadets who failed the depth perception portion of their pilot qualification test. In all 10 cases, we were able to get the cadets proficient enough to pass the test and they are now all pilots in the Air Force.

Dynamic visual acuity: As athletes move up the ranks from high school to college to the professional level, the game gets faster in every aspect. Therefore, having excellent dynamic visual acuity is just as important as having 20/20 static visual acuity.

Dynamic visual acuity is the ability to track moving objects, often while the athletes themselves are in motion. Picture a receiver running across the field while tracking the ball with the stands in the background.

To improve our athletes' tracking abilities, we use a variable speed rotator scanner, which has random numbers and letters on a 24-inch rotating disc. The letters are attached with Velcro so we can change their location each week. Athletes stand eight feet away from the rotating disc and identify as many digits and letters as they can per one-minute session. They need to move their eyes at the same speed as the disc to pick out the correct letter. We don't allow athletes to just fixate on one location and wait for the letters to come into view.

Results are recorded on a daily workout sheet, and once an athlete has correctly identified eight or more letters in a minute, they will train at a faster speed at their next session. We've found significant disparity in dynamic visual acuity performance among our athletes. Some of them rarely reach eight correct responses over multiple sessions, while others quickly improve their tracking ability and progress to higher speeds. Not surprisingly, most of the athletes in the latter group are our better on-field performers.

Accommodation: Several of our exercises work the accommodative process, which requires the eyes to maintain focus as they look back and forth from an object in the distance to one close to them, or as they track an object coming toward them. The accommodative system is important for any athlete who plays with a ball or puck, including a wide receiver running a route downfield who quickly turns his head to find the football or a hockey player trying to keep the puck on his stick as he looks up for a teammate to pass to.

One simple exercise we use is the near-far drill. A chart with 36-point type is posted on the wall while the athlete holds another chart with 9-point type. The athlete stands 20 feet from the wall while keeping the small chart four to six inches from their eyes, positioned directly below the wall chart in their path of vision. The athlete reads the top left letter from the wall chart out loud, then quickly refocuses to read the top left letter on the hand-held chart, and continues going back and forth between the charts for two 60-second sessions.

Visual memory: We believe sport-specific visual memory exercises develop more efficient processing of available visual information, which improves athletes' focus, concentration, and reaction skills. These drills are also fun because athletes can compete with one another.

One of our most competitive training exercises is the tachistoscope, which works to improve our athletes' focus and concentration. The tachistoscope consists of videos that flash action photos with sets of numbers embedded in them. The photos are flashed on a large screen for varying amounts of time, ranging from 130 to 1,000 milliseconds, and our athletes have to correctly identify and record the numbers they see.

A follow-up slide with the same image is shown with the answers so the athletes can immediately score their responses. Entire teams view the images together, making it a competitive situation in which teammates try to best one another.

This is another exercise in which we see a wide disparity among athletes. The tendency is for them to scan the screen from left to right rather than relax their eyes and take in the entire image at once. With practice, they learn to view the entire image and see the embedded numbers, and our best athletes are capable of processing three- or four-digit numbers at a flashing speed as fast as 130 milliseconds per image.

We also recently began using strobe glasses, which allow athletes to perform sport-specific activities (quarterback-receiver routes, basketball passes, baseball bat swings) with discontinuous visual input. This means they will only see the ball at various points in space, not continually. This forces an athlete's eyes to project where the ball is headed. They start at a quick LCD strobe speed and continue to slow the strobe down, which disrupts the visual image for longer.

So why should vision training be part of your athletes' regular training program? Well, why do athletes train for strength and power in the weightroom? Why do we stress proper nutrition to them? The answer is improved performance.

Do basketball coaches want their players shooting free throws that fall four inches short? Do volleyball coaches want their liberos to react late to high velocity spikes? Do ice hockey coaches want their goalies to be slow in picking up slap shots? Of course not! But remember, the body reacts only after the eyes send the proper information to the brain. Your athletes cannot hit, catch, or block something they don't see clearly.

FEEDBACK

Fascinating article!

My brother-in-law was on the Gold Medal hockey team in 1980. I remember Jim Craig and Steve Jensen (the goalies) telling me about the visual training they were doing all the way back then.

I have been using a brock string for a few years to help me better track the tennis ball. In addition, I have been doing accommodation exercises for several years to help with vertigo. Because I believe in this, I have been trying to figure out ways to implement visual training for my high-school tennis team. However, after reading this article it appears that the majority of this training is very high-tech and not available for most people. I am curious if there is a way to provide this type of training for my team.

- Joe Frasca, Liberty High-School



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